A dihybrid cross was done between tall round peas. Tall is dominant to short and round is dominant to wrinkled. What fraction of the offspring will be short and wrinkled.

a) 1/16
b) 3/16
c) 6/16
d) 9/16
e) None of these.

Answer is A. I get how they got it based on the 9:3:3:1 ratio for these types of crosses, but.........am I overthinking here? The question says a dihybrid cross was done between tall round peas, but it doesn't say that it was a heterozygous dihybrid cross (i.e. TtRr). Tall round can also mean TTRR or TtRR or TTRr. My question is: Is a dihybrid cross by default with a TtRr x TtRr (unless they specify something like "A homozygous dominant tall and heterozygous wrinkled pea is crossed with a heterozygous tall and heterozygous round pea")